[单选题]
A solenoid with 500 turns is 0.ohutfybr 10d+*9:;f *ndf w mf10 m long and carries a currend5/h 5h lc,ojft of 4.0 A. What strength of magnetic field will it have at itsl jo5 f5/hc,dh center?
A. $3.1 \; mT$
B. $6.2 \; mT$
C. $13 \; mT$
D. $25 \; mT$
